Internal combustion engine manufacturers are constantly seeking to increase power output of their products. One method of generally increasing engine power is to increase the compression ratio of the engine. Raising the compression ratio of an engine also generally raises the pressure and temperature within the combustion chamber during operation. Accordingly, various piston components must be capable of withstanding the increased stress of such operational conditions over the life of the engine.
To reduce the operating temperatures of piston components, a cooling gallery may be provided about a perimeter of the piston. Crankcase oil may be introduced to the cooling gallery, and may be distributed about the cooling gallery by the reciprocating motion of the piston, thereby reducing the operating temperature of the piston.
The heated oil may exit the cooling gallery through one or more holes that allow the oil to return to the crankcase. For example, oil may exit the cooling gallery though an opening adjacent the cylinder wall, between the piston head and the piston skirt. Some of this oil may become trapped between the piston skirt and the cylinder, and may further slip between the piston oil control rings and the cylinder wall into the combustion chamber. As a result, oil may be burned during the combustion process, resulting in increased oil consumption, build-up of carbon deposits in the engine, and fouling of engine emissions.
Accordingly, there is a need for a piston that minimizes the amount of oil that escapes from the cooling gallery into the combustion chamber.